Cooling system for internal combustion engine

ABSTRACT

A cooling system for an internal combustion engine includes a coolant flow passage through which coolant flows between the internal combustion engine and a heat exchanger, a flow amount control valve incorporated in the coolant flow passage and configured to control flow of the coolant flowing in the coolant flow passage, and a control section configured to effect switchover from a full opened state to a full closed state of the flow amount control valve based on a supply of a negative pressure produced in the internal combustion engine and to effect also switchover from the full closed state to the full opened state over a second period longer than a first period required for the switchover for the flow amount control valve from the full closed state to the full opened state, in response to stop of the supply of the negative pressure.

TECHNICAL FIELD

This invention relates to a cooling system for an internal combustionengine for controlling flow of coolant between the internal combustionengine and a heat exchanger.

BACKGROUND ART

Conventionally, an internal combustion engine, for realizing improvementof driving or fuel consumption efficiency under an optimal condition,promotes a warm-up operation at a cold time and implements a coolingoperation at a hot time. Specifically, when the temperature of coolantis low, control is effected not to flow the coolant to e.g. a radiator,thus promoting warm-up of the internal combustion engine; and when thetemperature of coolant is high, the coolant is allowed to flow to e.g.the radiator, thus controlling the temperature of the coolant to anoptimal temperature for fuel combustion. A technique usable in this typeof technique is disclosed in e.g. Patent Document 1.

A cooling water control valve disclosed in Patent Document 1 includes,in its casing, a valve body for controlling a flow amount of coolingwater (corresponding to “coolant” described above) and an actuator fordriving this valve body. The actuator is configured to be capable ofadjusting an opening degree of an opening portion of the valve body, foreffecting a flow amount control of the cooling water.

BACKGROUND ART DOCUMENT Patent Document

Patent Document 1: Japanese Unexamined Patent Application PublicationNo. 2013-249810

SUMMARY OF THE INVENTION Problem to be Solved by Invention

The technique disclosed in Patent Document 1 controls an opening portionof a valve body by a motor actuator, so flow amount adjustment ofcooling water can vary from a very small amount to a large flow amount.However, since the technique requires provision of the motor actuator,it can result in cost increase. Further, for fine adjustment of the flowamount, a sensor or the like needs to be provided for detecting theopening degree of the valve body. This can result in further increase ofthe cost.

Then, there is a need for a cooling system for an internal combustionengine that can control flow of coolant at a low cost.

Solution

According to a characterizing feature of a cooling system for aninternal combustion engine relating to the present invention, thecooling system comprises:

a coolant flow passage through which coolant flows between the internalcombustion engine and a heat exchanger;

a flow amount control valve incorporated in the coolant flow passage andconfigured to control flow of the coolant flowing in the coolant flowpassage; and

a control section configured to effect switchover from a full openedstate to a full closed state of the flow amount control valve based on asupply of a negative pressure produced in the internal combustion engineand to effect also switchover from the full closed state to the fullopened state over a second period longer than a first period requiredfor the switchover for the flow amount control valve from the fullclosed state to the full opened state, in response to stop of the supplyof the negative pressure.

With the above-described characterizing feature, the flow amount controlvalve can be controlled by a negative pressure produced in the internalcombustion engine. Thus, there is no need to additionally provide amotor actuator or an angle senor, etc. Thus, the flow (communication) ofcoolant can be controlled inexpensively. Further, with the abovearrangement, it is possible to delay the response in the switchover ofthe flow amount control valve from the full closed state to the fullopened state, as compared with a conventional flow amount control valve.Therefore, it is possible to prevent non-warmed coolant from flowing atone time altogether through the flow amount control valve, so thatre-cooling of once warmed-up internal combustion engine or coolant canbe suppressed.

Preferably, the system further comprises:

a switching valve for switching a pressure to be fed to the controlsection to either one of a first pressure comprised of the negativepressure produced in the internal combustion engine or a second pressurehigher than the first pressure; and a constricted portion forconstricting an opening area of a feed passage for feeding a fluidhaving the second pressure to the switching valve is incorporated in thefeed passage.

With the above-described arrangement, it is readily possible for theconstricted portion to realize a configuration for setting an openingarea of a feed passage for feeding fluid having the second pressuresmaller than an opening area of the feed passage for feeding fluidhaving the first pressure. Therefore, the above-described responserelating to the switchover from the full closed state to the full openedstate can be realized at low cost.

Still preferably, the control section is configured such that when theflow amount control valve is switched from the full closed state to thefull opened state, the control section firstly provides alternationbetween the full closed state and a released state of the full closedstate and then provides switchover to the full opened state.

With the above-described arrangement, the arrangement of delaying theresponse for the switchover from the full closed state to the fullopened state can be provided through control scheme.

Further preferably:

the flow amount control valve includes:

-   -   a communication passage for communicating an inlet port through        which the coolant enters the flow amount control valve to an        outlet port through which the coolant flows out of the flow        amount control valve; and    -   a bypass passage that communicates the inlet port to the outlet        port, with bypassing the communication passage; and

the control section firstly establishes communication between the inletport and the outlet port via the bypass passage and then establishescommunication between the inlet port and the outlet port via thecommunication passage.

With the above-described arrangement, prior to communication (flow) ofcoolant via the communication passage, communication of coolant can beestablished via the bypass passage. Therefore, by setting the flowamount of coolant that flows via the bypass passage smaller than theflow amount of coolant that flows via the communication passage, theabove-described arrangement of delaying response can be realized.Incidentally, such bypass passage can be realized by setting the flowamount area of the bypass passage smaller than that of the communicationpassage or by intermittent adjustment of the valve opening period of thebypass passage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a configuration of a cooling system for aninternal combustion engine,

FIG. 2 is a view showing one example of a flow amount control ofcoolant,

FIG. 3 is a diagram showing a configuration of a cooling system for aninternal combustion engine according to a further embodiment,

FIG. 4 is a view showing a flow amount control of coolant according tothe further embodiment,

FIG. 5 is a view showing a flow amount control of coolant according to astill further embodiment.

EMBODIMENTS

A cooling system for an internal combustion engine relating to thepresent invention controls flow (communication) of coolant by utilizinga negative pressure produced in the internal combustion engine. Next, acooling system 1 for an internal combustion engine of this embodiment(to be referred to simply as a “cooling system” hereinafter) will beexplained.

FIG. 1 is a block diagram schematically showing a configuration of thecooling system 1 relating to this embodiment. As shown in FIG. 1, thecooling system 1 includes a coolant flow passage 10, a flow amountcontrol valve 20, a control section 30 and a switching valve 40.

The coolant flow passage 10 communicates coolant between an internalcombustion engine 2 and a heat exchanger 3. Here, the “internalcombustion engine 2” refers to an engine mounted on a vehicle andconfigured to output power by combusting fuel such as gasoline, etc. The“heat exchanger 3” refers to a heater core for effecting heat exchangewith coolant. For instance, in case warm-up of the heat exchanger 3 isneeded at e.g. the time of start of the internal combustion engine 2,communication of the coolant to the heat exchanger 3 is stopped forpromoting the warm-up of this heat exchanger 3. With this, when warm-upof inside of a vehicle cabin is to be effected for instance, it ispossible to reduce a time period required until warm or hot air can besupplied into the vehicle cabin. On the other hand, when such warm-up ofthe heat exchanger 3 is not needed, coolant can be communicated to theheat exchanger 3 for cooling this heat exchanger 3.

Further, when cooling of the internal combustion engine 2 becomesnecessary, the coolant is communicated to a radiator 4 for cooling theinternal combustion engine 2. Such communications of coolant to the heatexchanger 3 or to the radiator 4 are effected by a water pump 5. And,according to a temperature of the coolant detected by a watertemperature sensor 6, a thermostat valve 7 is controlled to set whetherthe coolant is to be communicated to the heat exchanger 3 or to theradiator 4.

The flow amount control valve 20 is incorporated in the coolant flowpassage 10 and controls flow (communication) of the coolant to flow inthis coolant flow passage 10. As described above, the coolant flowpassage 10 communicates the coolant between the internal combustionengine 2 and the heat exchanger 3. The flow amount control valve 20 isincorporated in series within such coolant flow passage 10. Therefore,this flow amount control valve 20 is arranged such that the internalcombustion engine 2, the flow amount control valve 20 and the heatexchanger 3 are disposed in this mentioned order.

In this embodiment, the flow amount control valve 20 is configured toinclude a communication passage 21 and a bypass passage 22. Thecommunication passage 21 establishes communication between an inlet port23 and an outlet port 24. The inlet port 23 is a port trough which thecoolant enters (introduced) the flow amount control valve 20. The outletport 24 is a port through which the coolant flows out of (dischargedfrom) the flow amount control valve 20. Such communication passage 21corresponds to a main flow passage of the coolant that communicatesthrough the flow amount control valve 20.

On the other hand, the bypass passage 22 establishes communicationbetween the inlet port 23 and the outlet port 24 with bypassing thecommunication passage 21. There, the language “bypassing thecommunication passage 21” means that the coolant does not flow throughthe communication passage 21. Therefore, the bypass passage 22 isdisposed in juxtaposition with the communication passage 21, between theinlet port 23 and the outlet port 24. Such bypass passage 22 correspondsto an auxiliary flow passage of the coolant that flows in the flowamount control valve 20. The bypass passage 22 is configured such thatan opening area of this bypass passage 22 is smaller than an openingarea of the communication passage 21. For instance, advantageously, theopening area of the bypass passage 22 can be set to a fraction orone-few hundreds-th of the opening area of the communication passage 21.The bypass passage 22 is constituted of an electromagnetic valve 28whose opened/closed state is controlled by changing a position of a ballvalve 29 in response to an activation signal. Incidentally,advantageously, the flow amount control valve 20 can be a normallyopened type in view of fail-safe aspect, in order to prevent blocking ofcoolant communication in the event of a failure.

The control section 30 effects control of the opened/closed state of theflow amount control valve 20. Here, “control of the opened/closed stateof the flow amount control valve 20” means switchover from the fullopened state to the full closed state of the flow amount control valve20 as well as switchover from the full closed state to the full openedstate of the flow amount control valve 20. The control section 30effects such control based on a feeding state of a negative pressureproduced in the internal combustion engine 2. Here, “a negative pressureproduced in the internal combustion engine 2” means a pressure lowerthan the atmospheric pressure which will develop inside the cylinderwhen the piston is lowered during an intake stroke of the internalcombustion engine 2. Then, the control section 30 switches over the flowamount control valve 20 from the full closed state to the full openedstate based on (in response to) feeding of such negative pressure, orthe control section 30 switches over the flow amount control valve 20from the full opened state to the full closed state based on (inresponse to) stop of feeding of such negative pressure.

The control section 30 is configured to allow feeding of such negativepressure of the internal combustion engine 2 via the switching valve 40.This switching valve 40 is configured as a three-way valve, whichswitches the pressure to be fed to the control section 30 to either afirst pressure which comprises the above-described negative pressureproduced in the internal combustion engine 2 or to a second pressurehigher than the first pressure. Here, the first pressure is a pressurethat is lower than the atmospheric pressure and that is produced in theinternal combustion engine 2 as described above. The second pressure isa pressure higher than the pressure produced in the internal combustionengine 2. As such “second pressure”, the atmospheric pressure isemployed in this embodiment. The first pressure and the second pressureare fed to a control chamber 31 of the control section 30.

The control chamber 31 incorporates therein a spring member 32 and avalve body 33. When the first pressure is fed to the control chamber 31,the valve body 33 is moved toward a pressure feed opening 34 side of thecontrol chamber 31 against an urging force of the spring member 32. Inresponse to this, a link mechanism 35 is rotated about a rotational axisto rotate a spherical-faced valve 25 of the flow amount control valve 20inside the valve chamber 26. With this, an opening portion 27 of thecommunication passage 21 is closed by the spherical-faced valve 25, thussetting the flow amount control valve 20 into the full closed state.

On the other hand, when the second pressure is fed to the controlchamber 31, the valve body 33, as being urged by the spring member 32,is moved to the far side of the control valve 31. With this, the linkmechanism 35 is rotated about the rotational axis to rotate thespherical-faced valve 25 of the flow amount control valve 20 inside thevalve chamber 26. With this, the spherical-faced valve 25 is moved awayfrom the opening portion 27 of the communication passage 21, whereby theflow amount control valve 20 is set to the full opened state.

Here, the flow amount control valve 20 can be switched over from thefull closed state to the full opened state only by stopping feeding ofthe first pressure. If a period required for switching the flow amountcontrol valve 20 from the full closed state to the full opened state bysuch stopping of feeding of the first pressure is defined as “firstperiod”. In this embodiment, the control section 30 is configured torequire a “second period” longer than the first period for switching theflow amount control valve 20 from the full closed state to the fullopened state. Namely, the control section 30 firstly establishescommunication of coolant between the inlet port 23 and the outlet port24 via the bypass passage 22 which is the auxiliary passage beforeestablishing communication of the coolant to the communication passage21 which is the main passage and then establishes communication betweenthe inlet port 23 and the outlet port 24 via the communication passage21.

Therefore, the establishment of communication between the inlet port 23and the outlet port 24 via the bypass passage 22 takes longer than theperiod (first period) required for direct establishment of communicationbetween the inlet port 23 and the outlet port 24 via the communicationpassage 21, by a period required for the establishment of communicationbetween the inlet port 23 and the outlet port 24 via the bypass passage22. With this arrangement, it is possible to suppress occurrence ofinconvenience of cooling of the internal combustion engine 2 withintroduction of coolant having a lower temperature than the temperatureof this internal combustion engine after warm-up, in spite of thisinternal combustion engine 2 being actually warmed up. Incidentally, itis possible to arrange such that coolant may be communicated also to thebypass passage 22 or not communicated to this bypass passage 22, whencoolant is flowing in the communication passage 21.

Next, a mode of the flow amount control of coolant by the cooling system1 will be explained. FIG. 2 shows an example of the flow amount controlmode. In this FIG. 2, the vertical represents a flow amount of coolantthat flows out of the flow amount control valve 20 and the horizontalaxis represents a time period. As described above, the flow amountcontrol valve 20 is a normally opened type. Therefore, this valve 20 ismaintained under its full opened state until the internal combustionengine 2 is started at t=t1.

When the internal combustion engine 2 is started at t=t1, the firstpressure as a negative pressure produced in the internal combustionengine 2 is fed to the control section 30. In response to this, the flowamount control valve 20 is switched over from the full opened state tothe full closed state (t=t2). At this time, the thermostat valve 7 toois under its closed state, so no communication of coolant takes place.Thus, warm-up of the internal combustion engine 2 is promoted.

Upon completion of the warm-up of the internal combustion engine 2(t=t3), an activation signal is inputted to the electromagnetic valve28, thus allowing communication of coolant to the bypass passage 22.With this, coolant is communicated to the bypass passage 22. As thecoolant is communicated also to the internal combustion engine 2 underthis state, heat will be equalized over the entire internal combustionengine 2 (t=t3-t4). Thereafter, in order to effect heat exchange betweenthe coolant and the heat exchanger 3, the feeding of the first pressureto the control chamber 31 of the control section 30 is stopped, wherebythe second pressure (e.g. the atmospheric pressure) higher than thefirst pressure is fed. In response to this, the flow amount controlvalve 20 is shifted to the full opened state (t=t5). Further, coolant iscommunicated also to the radiator 4 depending on the temperature of thiscoolant, whereby the internal combustion engine 2 is cooled.

In this way, according to this cooling system 1, when the flow amountcontrol valve 20 is to be switched over from the full closed state tothe full opened state, during t3-t4, firstly, coolant is communicatedvia the bypass passage 22 as the auxiliary passage by an amountsufficiently smaller than the flow amount of coolant by thecommunication passage 21 as a main flow passage; thereafter, the coolantis communicated via the communication passage 21. Therefore, incomparison with a period (first period) required for switchover of theflow amount control valve 20 from the full closed state to the fullopened state, which is the arrangement of communicating the coolant viathe communication passage 21 alone, the flow amount control valve 20 isswitched over from the full closed state to the full opened state,taking a longer period (second period).

Other Embodiments

In the foregoing embodiment, it was explained that the flow amountcontrol valve 20 includes the communication passage 21 and the bypasspassage 22. Alternatively, the flow amount control valve 20 may notinclude the bypass passage 22. FIG. 3 is a block diagram schematicallyshowing such modified configuration of the cooling system 1.

In this embodiment, since the bypass passage 22 is not provided in theflow amount control valve 20, the electromagnetic valve 28 forcontrolling communication state of this bypass passage 22 is notprovided, either. On the other hand, a constricted portion 42 isprovided in a feed passage 41 through which the second pressure (e.g.the atmospheric pressure) is fed to the switching valve 40. Thisconstricted portion 42 constricts the opening area of the feed passage41. Such constricted portion 42 can be constituted of a known orificefor example, or can be constituted of a valve for adjusting the openingarea. With this, the period until the control chamber 31 is filled withfluid having the atmospheric pressure is set longer than the perioduntil the control chamber 31 is filled with the atmospheric pressurefluid in case no such constricted portion 42 is provided in the feedpassage 41. Namely, as indicated by t4-t5 in FIG. 4, the period untilthe flow amount control valve 20 is switched over from the full closedstate to the full opened state can be extended. Thus, like the foregoingembodiment, the switchover of the flow amount control valve 20 from thefull closed state to the full opened state can proceed gradually, sothat the heat in the internal combustion engine 2 can be rendereduniform.

Further, the control section 30 can be alternatively configured suchthat when the flow amount control valve 20 is switched from the fullclosed state to the full opened state, the control section 30 firstlyalternates between the full closed state and a released state of thefull closed state and thereafter switches to the full opened state. Withthis configuration, as shown in FIG. 5, during t3-t4, the full closedstate and the released state that allows slight communication of coolantare alternated (effected for a plurality of times) so as to temporarilyallow a flow amount sufficiently smaller than the flow amount of coolantunder the full opened state, and thereafter the full opened state isprovided, whereby the temperature variation of the internal combustionengine 2 can be made small like the foregoing embodiment.

INDUSTRIAL APPLICABILITY

The present invention can be applied to a cooling system for an internalcombustion engine for controlling flow of coolant between the internalcombustion engine and a heat exchanger.

DESCRIPTION OF REFERENCE MARKS/NUMERALS

1: cooling system (cooling system of internal combustion engine)

2: internal combustion engine

3: heat exchanger

10: coolant flow passage

20: flow amount control valve

21: communication passage

22: bypass passage

23: inlet port

24: outlet port

30: control section

40: switching valve

41: feed passage

42: constricted portion

1. A cooling system for an internal combustion engine, the coolingsystem comprising: a coolant flow passage through which coolant flowsbetween the internal combustion engine and a heat exchanger; a flowamount control valve incorporated in the coolant flow passage andconfigured to control flow of the coolant flowing in the coolant flowpassage; and a control section configured to effect switchover from afull opened state to a full closed state of the flow amount controlvalve based on a supply of a negative pressure produced in the internalcombustion engine and to effect also switchover from the full closedstate to the full opened state over a second period longer than a firstperiod required for the switchover for the flow amount control valvefrom the full closed state to the full opened state, in response to stopof the supply of the negative pressure.
 2. The cooling system for aninternal combustion engine of claim 1, wherein: the system furthercomprises a switching valve for switching a pressure to be fed to thecontrol section to either one of a first pressure comprised of thenegative pressure produced in the internal combustion engine or a secondpressure higher than the first pressure; and a constricted portion forconstricting an opening area of a feed passage for feeding a fluidhaving the second pressure to the switching valve is incorporated in thefeed passage.
 3. The cooling system for an internal combustion engine ofclaim 1, wherein the control section is configured such that when theflow amount control valve is switched from the full closed state to thefull opened state, the control section firstly provides alternationbetween the full closed state and a released state of the full closedstate and then provides switchover to the full opened state.
 4. Thecooling system for an internal combustion engine of claim 1, wherein:the flow amount control valve includes: a communication passage forcommunicating an inlet port through which the coolant enters the flowamount control valve to an outlet port through which the coolant flowsout of the flow amount control valve; and a bypass passage thatcommunicates the inlet port to the outlet port, with bypassing thecommunication passage; and the control section firstly establishescommunication between the inlet port and the outlet port via the bypasspassage and then establishes communication between the inlet port andthe outlet port via the communication passage.